How to Read a Map: A Practical Guide for Walking in Ireland
How to Read a Map: A Practical Guide for Walking in Ireland
Map reading is the skill that transforms a self-guided walk from anxious to enjoyable. When you can look at a piece of paper and understand exactly where you are, where the ground rises, where the bog starts and where the path threads through — the landscape opens up in a way that no GPS screen quite replicates.
We've been designing self-guided walking holidays in Ireland for years. Our walkers navigate Ireland's trails independently every week, carrying route notes and their own maps, making their own decisions on the ground. Here is the map-reading foundation that serves them well — from understanding scale and symbols to taking a compass bearing on a foggy Wicklow plateau.
Note: this guide focuses on OSi (Ordnance Survey Ireland) maps, which are the maps used on Ireland's walking routes. If you're planning a walk in Britain, you'll use OS (Ordnance Survey) maps from a different publisher — the grid system and some symbols differ, though the core principles are identical.
Understanding map scale — what 1:50,000 actually means
Every map has a scale. The scale tells you the relationship between distance on the map and distance on the ground.
The map walkers use most often on Ireland's waymarked trails is the OSi Discovery Series at 1:50,000. That ratio means one unit on the map equals 50,000 of the same unit in the real world. In practical terms: 1 cm on a 1:50,000 map equals 500 metres on the ground. 2 cm equals 1 kilometre.
Once you have that in your head, distance estimation becomes quick. The Kerry Way stage from Killarney to Glencar is roughly 20 km. On your 1:50,000 map, that's about 40 cm of paper — the length of your forearm.
OSi also produces a 1:25,000 Activity Series for some popular areas. At this scale, 1 cm equals 250 metres — the map shows twice as much detail, which is useful in complex or mountainous terrain. For most multi-day routes, the 1:50,000 Discovery Series is the right choice. For detailed navigation in the Wicklow Mountains or on Carrauntoohil, the 1:25,000 is worth carrying.
Map symbols and colours — what everything means
OSi maps use a consistent colour and symbol system. Once you know the key ones, the map becomes readable at a glance.
Colours:
- Blue — water: rivers, lakes, streams, the coast. Anything blue is wet.
- Green — vegetation: woodland, forestry, hedgerows.
- Brown — terrain: contour lines showing height and shape of the ground.
- Black — man-made features: buildings, roads, walls, fences, paths.
- Yellow — open land: rough pasture, heath, bog. On Irish walking routes, yellow is often where you're walking.
- White — open upland, rock, or area without dense vegetation.
Symbols walkers look for most:
- Dotted or dashed lines — footpaths and tracks, not surfaced roads
- Green or orange diamonds — waymarked walking routes
- Triangles — trig points (surveyed summits)
- Cliff hatching — steep rocky ground you don't want to cross
- Blue hatching — marsh or wet ground worth avoiding
- Crosses — churches, ruins, historic sites
Every OSi map has a full legend on the reverse. Spend five minutes with it before your first walk. After a few days on trail, the symbols become second nature.
How to read contour lines
Contour lines are the most important thing on a walking map — and the most misunderstood.
A contour line connects all points at the same height above sea level. On OSi 1:50,000 maps, each contour line is 10 metres apart in altitude. Where lines are close together, the ground is steep — you're climbing or descending quickly. Where lines are widely spaced, the ground is gentle.
A few patterns to learn:
V-shapes pointing uphill — a valley. Water flows towards the point of the V.
V-shapes pointing downhill — a ridge or spur. The ground rises towards the point.
Closed circles or ovals — a hill summit or knoll. The innermost circle is the highest point.
Evenly spaced parallel lines — a uniform slope, steady climbing.
Lines that seem to merge or bunch — a cliff or very steep ground. On some OSi maps, cliff symbols replace contours in the steepest sections.
A practical example: look at the Wicklow Way route across the ridge above Lough Tay. The contours are tightly packed on both sides of the ridge with a slightly wider gap at the crest — a classic narrow ridge between two steep slopes. That's exactly what you'll feel underfoot.
Grid references — how the Irish system works
Grid references let you pinpoint an exact location on a map and communicate it to someone else — or find a specific location someone has given you.
Ireland uses the ITM (Irish Transverse Mercator) grid system. If you're used to the British National Grid, the principle is the same but the numbers differ — don't mix them up.
On OSi maps, the grid is printed as faint blue lines across the map face, labelled with numbers along the edges. To read a six-figure grid reference:
1. Find the grid square your location is in. 2. Read the number on the left edge (easting) of that square — this is the first two digits of your reference. 3. Estimate how far across the square your point is (0–9 tenths) — this is your third digit. 4. Read the number on the bottom edge (northing) of that square — digits four and five. 5. Estimate how far up the square your point is (0–9 tenths) — digit six.
The memory aid used in every navigation course: along the corridor, up the stairs. Read across (easting) first, then up (northing).
A six-figure reference pinpoints you to within about 100 metres. For more precision, use an eight-figure reference — the same method, with one extra digit for each direction.
On modern phones, the OSi Maps app shows your ITM coordinates in real time, which is a useful cross-check. But learning to read a paper grid reference means you can navigate without battery, signal, or screen glare.
How to orient your map
Orienting your map means turning it until it matches the landscape around you — north on the map pointing to actual north, and the features on the map lining up with the features you can see.
This sounds obvious. But it's remarkable how many people walk with a map turned so the place names read correctly to them — which means they're reading the map upside down relative to the ground, and every turn they deduce is backwards.
The landmark method (easiest):
Find a clear feature you can see on the ground — a lake, a road junction, a summit. Find it on the map. Rotate the map until those features line up with their real-world positions around you. The map is now oriented.
The compass method (more reliable in featureless terrain):
Place your compass on the map with the edge along the north-south grid lines, dial set to north. Rotate the entire map-and-compass together until the compass needle points to north. The map is now oriented to magnetic north — close enough for walking navigation.
Once the map is oriented, every direction on the map matches your surroundings. If the path turns left on the map, it turns left in front of you.
Using a compass with your map
On a clear day in waymarked terrain, a compass stays in your pocket. On a foggy plateau with no landmarks visible — the Sally Gap in October mist, Lugnaquilla in cloud — a compass is what gets you to where you're going.
The parts of a walking compass you actually use:
- Baseplate — the transparent rectangular base, with a direction-of-travel arrow
- Bezel — the rotating outer ring, marked in degrees 0–360
- Magnetic needle — the red end points to magnetic north
- Orienting lines — lines inside the bezel aligned with the needle when set
Taking a bearing from the map — five steps:
1. Place the edge of your compass on the map between your current position and your destination. 2. Rotate the bezel until the orienting lines run parallel to the north-south grid lines, with north on the bezel pointing to the top of the map. 3. Lift the compass off the map. Hold it level in front of you. 4. Rotate your body until the red magnetic needle sits inside the orienting arrow ("red in the shed"). 5. The direction-of-travel arrow now points at your destination. Walk that way.
Magnetic declination in Ireland: The compass points to magnetic north, not true (grid) north. In Ireland the difference is currently about 2–3 degrees west — small enough that for most walking navigation you can safely ignore it. If you're doing very precise navigation over long distances, apply the correction.
Which OSi map do I need for Ireland's main walking routes?
One question we get regularly: which map should I buy before my walk?
The OSi Discovery Series covers all of Ireland in 89 sheets. Each sheet covers roughly 60 × 75 km. Multi-day routes span several sheets, which is why WHI route notes include the relevant sheet numbers.
Kerry Way: Discovery Series sheets 78, 83, 84, 85. Alternatively, OSi publish a dedicated Kerry Way map — one sheet covers the full route.
Wicklow Way: Discovery Series sheets 50, 56, 62. The northern mountain section (sheets 50 and 56) is the most navigationally complex.
Dingle Way: Discovery Series sheets 70, 71.
Barrow Way: Discovery Series sheet 61, with sheet 68 for the southern section.
Connemara / Western Way: Sheets 37, 38, 44.
OSi maps are available from outdoor shops, tourist offices and directly from the OSi website (osi.ie). Budget around €12–15 per sheet.
On all our self-guided walking holidays, we provide detailed route notes covering every stage — but we always recommend carrying the relevant OSi map. It is your safety net, your context, and — once you can read it — your best companion on the trail.
Frequently asked questions
What is the difference between an OS map and an OSi map?
OS (Ordnance Survey) publishes maps for Great Britain. OSi (Ordnance Survey Ireland) publishes maps for the Republic of Ireland. They use different grid systems — the British National Grid vs. the Irish Transverse Mercator — and have some differences in symbology. Walkers planning routes in the Republic of Ireland need OSi maps. Northern Ireland is covered by OS (OSNI — Ordnance Survey Northern Ireland).
What does 1:50,000 mean on a map?
It means 1 unit on the map equals 50,000 of the same unit in reality. So 1 cm on a 1:50,000 map equals 500 metres on the ground; 2 cm equals 1 kilometre. The OSi Discovery Series — used on Ireland's waymarked trails — is 1:50,000. A 1:25,000 map shows twice as much detail and is useful for complex terrain.
How do you read map contour lines?
Contour lines connect points of equal height. On OSi 1:50,000 maps, each line represents 10 metres of elevation. Closely spaced lines mean steep ground; widely spaced lines mean gentle terrain. V-shapes pointing uphill indicate a valley; V-shapes pointing downhill indicate a ridge. Closed oval or circular patterns indicate a hilltop.
Do I need a compass as well as a map?
For Ireland's waymarked trails in good visibility, route notes and a map are usually sufficient — the routes are well signed and the terrain is readable. A compass becomes essential in poor visibility, on exposed plateaus (Wicklow Mountains, the Lugnaquilla approaches, the Maumturks), and anywhere the terrain is featureless. If you're doing any off-trail walking, always carry a compass and know how to use it.
Walking Ireland's trails
The walkers who get the most from Ireland's long-distance routes are those who walk with the map open, reading the landscape ahead rather than just following arrows. When you can look at the hillside in front of you and confirm what the contours told you it would be — the climb sharpens into a ridge, the valley opens exactly where you expected — the walk becomes something more than exercise.
If you'd like to experience Ireland's trails at your own pace — luggage carried between overnight stops, accommodation booked, route notes prepared — browse our self-guided walking holidays. The Kerry Way and Wicklow Way are two routes where good map reading will add enormously to every day on the trail.
